The present invention relates to a rotary servo valve that carries out flow rate control and pressure control in the hydraulic circuit of each industrial machinery and punch press liquid operated servo system using the same valve.
To the liquid operated servo system in conventional technological field of hydraulic control type machine tools and industrial machinery, directly driven type servo valves or electromagnetic proportional control servo valves, and other control valves are popularly used.
For example, in hydraulically driven punch presses, the elevating stroke of hydraulic cylinder ram is controlled in four patterns of quick approach stroke, low-speed punching stroke, high-speed descending stroke at the time of chip shaking off, and quick return stroke in order to achieve low noise and low vibration.
In order to control the strokes of the above-mentioned four patterns, as depicted in the hydraulic circuit shown in FIG. 1, a high pressure hydraulic pump 207 and low pressure hydraulic pump 209 are installed via the suction filter 205 from the oil tank 203 in order to operate the hydraulic cylinder 201. The high pressure pipe conduit 211 and the low pressure pipe conduit 213 on the discharge ends of the high pressure hydraulic pump 207 and the low pressure hydraulic pump 209 are connected to high-low pressure selector valve 215, and the discharge end of this high-low pressure selector valve 215 is connected to the upper oil chamber 219 and the lower oil chamber 221 of the hydraulic cylinder 201 via the upper-lower selector valve 217.
In the midway of the high-pressure pipe conduit 211 and the low-pressure pipe conduit 213, high-pressure accumulator 223, low-pressure accumulator 225, and other control valves are installed.
In the above-mentioned hydraulic circuit, low-pressure high-flow rate hydraulic fluid is controlled to be supplied to the hydraulic cylinder 201 in the quick approach, quick return, and chip shake-off strokes, and the high-pressure small-flow rate hydraulic fluid to be supplied in the punching stroke.
Now, in the above-mentioned conventional control system, a high-low pressure selector valve 215 is required for changing over high and low hydraulic pressures to operate the hydraulic cylinder 201, and the upper-lower selector valve 217 is required for changing over the top and the bottom of the hydraulic cylinder 201. In this way, one or more control valves are required for one circuit, and the circuit increases the complexity. Consequently, there is a problem in that the particularly subtle control is difficult.
In addition, a space for installing a plurality of valves 215, 217 is required, causing a problem of preventing size reduction of the system, and an increase of valves 215, 217 tends to increase the risk of oil leak, and causes a problem of energy loss.
Furthermore, hydraulic piping and electrical wiring for operating valves 215, 217 are required, respectively, causing a problem of increased complexity of the system.
The hydraulic manifold to which the two servo valves (215, 217) are installed requires a hydraulic circuit of two systems of high pressure and low pressure and a two-way circuit of rise and descend, making the hydraulic manifold circuit extremely complicated and resulting in a large profile, interfering the system from reducing the size.
In the directly operated servo valve or electromagnetic proportional servo valve, a method for detecting displacement of the built-in spool with a differential transformer and feeding back of the detected result to the spool displacement instruction signals is used. However, because the differential transformer adopts a detection principle using coils, the detection displacement is shifted (temperature is drifted) by the ambient air temperature, and detection errors are generated, making it difficult to achieve high-accuracy spool position control.
Because in the valve manufacturing process, there is an individual difference between processing sizes of the valve main body and the spool of the servo valve, a difference is generated in the opening initiation position of the hydraulic fluid supply port as well as the relation between the spool displacement rate and the supply flow rate, and in the conventional liquid operated servo system with two servo valves combined, there is a problem of different flow rate characteristics for each servo system. In addition, when two servo valves are combined, the oil passage connecting the two servo valves becomes long and the response speed of the valve to the control instructions becomes slow.
Accordingly, the present invention has been made to solve the problems as described above, and it is an object of the present invention to provide a compact and high-accuracy rotary servo valve equipped with both supply fluid selector capabilities and the flow rate control capabilities as well as the punch press liquid operated servo system using the said valve.
To achieve the above object, a rotary servo valve according to the first aspect comprises a valve main body provided with a plurality of intake ports for taking in a plurality of pressure fluids which have pressures different to one another and a plurality of supply ports for supplying a plurality of pressure fluids taken in to the desired drives; a spool which is installed free to reciprocate along a sliding groove formed in the valve main body while being free to rotate around the longitudinal direction of the sliding groove and which allows one of the plurality of intake ports to selectively communicate with one of the plurality of supply ports; reciprocatedly moving mechanisms for reciprocating the spool along the sliding groove without rotating; and rotating mechanisms for rotating the spool along the sliding groove without reciprocating.
The rotary servo valve according to the second aspect is a rotary servo valve according to the first aspect, wherein the plurality of intake ports includes a high-pressure opening for taking in high-pressure fluid and a low-pressure opening for taking in low-pressure fluid, and the plurality of supply ports includes a descent port for supplying pressure fluid to the upper chamber of the cylinder operated by the pressure fluid and a rise port for supplying pressure fluid to the lower chamber of the cylinder.
The rotary servo valve according to the third aspect is a rotary servo valve according to the first aspect, wherein one of the plurality of intake ports is selected by the reciprocating motion of the spool and one of the plurality of supply ports is selected by the rotating motion of the spool.
The rotary servo valve according to the fourth aspect is a rotary servo valve according to the first aspect, wherein one of the plurality of supply ports is selected by the reciprocating motion of the spool and one of the plurality of intake ports is selected by the rotating motion of the spool.
The rotary servo valve according to the fifth aspect is a rotary servo valve according to the first aspect, further comprising a means for detecting a rotation angle of the spool.
The rotary servo valve according to the sixth aspect is a rotary servo valve according to the fifth aspect, wherein the means for detecting the rotation angle is a rotary encoder.
To achieve the above object, a punch press hydraulic servo system according to the seventh aspect comprises a plurality of pressure sources for supplying a plurality of pressure fluids with pressures different from one another; a punch press hydraulic cylinder; a valve main body provided with a plurality of intake ports for taking in a plurality of pressure fluids and a plurality of supply ports for supplying the plurality of pressure fluids taken in to an upper chamber or a lower chamber of a hydraulic cylinder; a spool which is installed free to reciprocate along a sliding groove equipped to the valve main body while being free to rotate around the longitudinal direction of the sliding groove and which allows one of the plurality of intake ports to selectively communicate with one of the plurality of supply ports; and control means for independently controlling the reciprocating motion and the rotating motion of the spool, wherein by the control of the control means for the spool, one of the plurality of intake ports and one of the plurality of supply ports are selected to supply pressure fluid having a desired pressure to either the upper chamber or the lower chamber of the hydraulic cylinder, and at the same time, the rotating motion of the spool is subtly adjusted to adjust a flow rate of the pressure fluid supplied to the upper chamber or the lower chamber of the hydraulic cylinder, and thereby driving speed and power of the piston of the hydraulic cylinder are controlled.
The punch press hydraulic servo system according to the eighth aspect is a punch press hydraulic servo system according to the seventh aspect, further comprising a means for detecting a rotation angle of the spool.
The punch press hydraulic servo system according to the ninth aspect is a punch press hydraulic servo system according to the eighth aspect, wherein the means for detecting the rotation angle is a rotary encoder.
To achieve the above object, a rotary servo valve according to the tenth aspect comprises a valve main body provided with a plurality of intake ports for taking in a plurality of pressure fluids which have pressures different to one another and a plurality of supply ports for supplying a plurality of pressure fluids taken in to the desired drives; a first rotating spool that has a hollow, and is installed to be inserted into the valve main body while being free to rotate, and selectively allows one of the plurality of intake ports to communicate with the hollow; a first rotating actuator for rotating the first rotating spool; a second rotating spool that has a hollow, and is installed to be inserted into the valve main body while being free to rotate, and selectively allows one of the plurality of supply ports to communicate with the hollow; and a second rotating actuator for rotating the second rotating spool, wherein the valve main body has a connection passage that interconnects pressure fluids in the hollows of the first and the second rotating spools.
The rotary servo valve according to eleventh aspect is a rotary servo valve according to the tenth aspect, wherein the plurality of intake ports includes a high-pressure opening for taking in high-pressure fluid and a low-pressure opening for taking in low-pressure fluid, and the plurality of supply ports includes a descent port for supplying pressure fluid to the upper chamber of the cylinder operated by the pressure fluid and a rise port for supplying pressure fluid to the lower chamber of the cylinder.
The rotary servo valve according to twelfth aspect is a rotary servo valve according to the tenth aspect, wherein a hollow wall of the first rotating spool is provided with a first opening section that is allowed to selectively communicate with the plurality of intake ports and a second opening section that communicates with the connection passage of the valve main body, and the second rotating spool is provided with a hollow pressure fluid flow-in chamber and a pressure fluid discharge chamber, and the pressure fluid flow-in chamber is provided with a third opening section that communicates with the connection passage and a fourth opening section that is allowed to selectively communicate with a descent port and a rise port that respectively communicates with the upper chamber and the lower chamber of the cylinder, and the pressure fluid discharge chamber is provided with a fifth opening section that is allowed to selectively communicate with a discharge-side descent port and a discharge-side rise port that respectively communicates with the descent port and the rise port through first and second connection passages and a sixth opening section that communicates with an oil drain port that connects to an oil tank.
The rotary servo valve according to the thirteenth aspect is a rotary servo valve according to the tenth aspect, wherein a hollow wall of the first rotating spool is provided with a first opening section that is allowed to selectively communicate with the plurality of intake ports and a second opening section that communicates with the connection passage of the valve main body, and the second rotating spool is provided with a hollow pressure fluid flow-in chamber and a pressure fluid discharge chamber, and the pressure fluid flow-in chamber is provided with a third opening section that communicates with the connection passage and a fourth opening section that is allowed to selectively communicate with a descent port and a rise port that respectively communicates with the upper chamber and the lower chamber of the cylinder, and the pressure fluid discharge chamber is provided with a fifth opening section that is allowed to selectively communicate with a discharge-side descent port and a discharge-side rise port that respectively communicates with a lower oil drain port and an upper oil drain port that are respectively located at the upper chamber and the lower chamber of the cylinder, and a sixth opening section that communicates with an oil drain port that connects to an oil tank.
To achieve the above object, a rotary servo valve according to the fourteenth aspect comprises a valve main body provided with a plurality of intake ports for taking in a plurality of pressure fluids which have pressures different to one another and a plurality of supply ports for supplying a plurality of pressure fluids taken in to the desired drives; a first sliding spool that has a hollow, and is installed to be inserted into the valve main body while being free to reciprocate, and selectively allows one of the plurality of intake ports to communicate with the hollow; a first sliding actuator for sliding the first sliding spool; a second sliding spool that has a hollow, and is installed to be inserted into the valve main body while being free to reciprocate, and selectively allows one of the plurality of supply ports to communicate with the hollow; and a second sliding actuator for sliding the second sliding spool, wherein the valve main body has a connection passage that interconnects pressure fluids in the hollows of the first and the second sliding spools.
The rotary servo valve according to the fifteenth aspect is a rotary servo valve according to the fourteenth aspect, wherein the plurality of intake ports includes a high-pressure openings for taking in high-pressure fluid and low-pressure openings for taking in low-pressure fluid, and the plurality of supply ports includes a descent port for supplying pressure fluid to the upper chamber of the cylinder operated by the pressure fluid and a rise port for supplying pressure fluid to the lower chamber of the cylinder.
The rotary servo valve according to the sixteenth aspect is a rotary servo valve according to the fourteenth aspect, wherein a hollow wall of the first sliding spool is provided with a first opening section that is allowed to selectively communicate with the plurality of intake ports and a second opening section that communicates with the connection passage of the valve main body, and the second sliding spool is provided with a hollow pressure fluid flow-in chamber and a pressure fluid discharge chamber, and the pressure fluid flow-in chamber is provided with a third opening section that communicates with the connection passage and a fourth opening section that is allowed to selectively communicate with a descent port and a rise port that respectively communicates with the upper chamber and the lower chamber of the cylinder, and the pressure fluid discharge chamber is provided with a fifth opening section that is allowed to selectively communicate with a discharge-side descent port and a discharge-side rise port that respectively communicates with the descent port and the rise port through first and second connection passages and a sixth opening section that communicates with an oil drain port that connects to an oil tank.
The rotary servo valve according to the seventeenth aspect is a rotary servo valve according to the fourteenth aspect, wherein a hollow wall of the first sliding spool is provided with a first opening section that is allowed to selectively communicate with the plurality of intake ports and a second opening section that communicates with the connection passage of the valve main body, and the second sliding spool is provided with a hollow pressure fluid flow-in chamber and a pressure fluid discharge chamber, and the pressure fluid flow-in chamber is provided with a third opening section that communicates with the connection passage and a fourth opening section that is allowed to selectively communicate with a descent port and a rise port that respectively communicates with the upper chamber and the lower chamber of the cylinder, and the pressure fluid discharge chamber is provided with a fifth opening section that is allowed to selectively communicate with a discharge-side lowering port and a discharge-side rise port that respectively communicates with a lower oil drain port and an upper oil drain port that are respectively located at the upper chamber and the lower chamber of the cylinder, and a sixth opening section that communicates with an oil drain port that connects to an oil tank.